HIGH-PRESSURE NEUROLOGICAL SYNDROME (HPNS)

High-pressure neurological syndrome (HPNS) is a condition encountered in diving beyond a depth of 100 m. Manifestations include headache, tr emor, myoclonus, neuropsychiatric disturbances and EEG changes. Convul sions are seen only in experimental animals. Most of the changes are r eversible on surfacing but some such as memory disturbances may linger on for long periods. Excessive atmospheric pressure is the most impor tant factor in the pathogenesis of HPNS. Neurotransmitter changes occu r of which serotonin appears to be a more likely mediator because of t he resemblance of HPNS to serotonin syndrome. Anesthetics and anticonv ulsants have been used in experimental animals but are unsuitable for use in human divers. Breathing gas mixtures such as heliox have enable d the extension of depth of diving without HPNS. Use of 5-HT1A recepto r antagonists may provide an interesting approach to prevention of HPN S.